Texas horned lizard

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Texas horned lizard
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Iguania
Family: Phrynosomatidae
Genus: Phrynosoma
P. cornutum
Binomial name
Phrynosoma cornutum
(Harlan, 1825)

Agama cornuta Harlan, 1825

The Texas horned lizard (Phrynosoma cornutum) is one of about 14 North American species of spikey-bodied reptiles called horned lizards. P. cornutum ranges from Colorado and Kansas to northern Mexico (in the Sonoran desert), and from southeastern Arizona to Texas. [2] Also, isolated, introduced populations are found in the Carolinas, Georgia, and northern Florida. [3] Texas horned lizards may also be native to Louisiana [4] and Arkansas. [5]

North America Continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.

In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies.

Reptile class of animals

Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.



The horned lizard is popularly called a "horned toad", or "horned frog", but it is neither a toad nor a frog. The popular names come from the lizard's rounded body and blunt snout, which give it a decidedly batrachian appearance. [6] Phrynosoma literally means "toad-bodied" and cornutum means "horned". [7] [8] The lizard's horns are extensions of its cranium and contain true bone.

Horned lizard genus of reptiles

Horned lizards (Phrynosoma), also known as horny toads or horntoads, are a genus of North American lizards and the type genus of the family Phrynosomatidae. The common names refer directly to their flattened, rounded body and blunt snout.

Toad amphibian

Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands.

Frog Order of amphibians

A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura. The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforests. There are over 7,000 recorded species, accounting for around 88% of extant amphibian species. They are also one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history.


The Texas horned lizard is the largest-bodied and most widely distributed of the roughly 14 species of horned lizards in the western United States and Mexico. The average Texas horned lizard is 69 mm (2.7 in) in snout-vent length, [9] but the upper boundary for males is 94 mm (3.7 in) and for females it is 114 mm (4.5 in). [10]

Defensive behavior

Although its coloration generally serves as camouflage against predation, when threatened by a predator, a horned lizard puffs up and appears very fat, which causes its body scales to protrude, making it difficult to swallow. The Texas horned lizard, along with at least three other species of the genus Phrynosoma , also has the ability to squirt an aimed stream of blood from the corners of the eyes and sometimes from its mouth for a distance up to 5 ft (1.5 m). They do this by restricting the blood flow leaving the head, thereby increasing blood pressure and rupturing tiny vessels around the eyelids. This not only confuses would-be predators, but also the blood is mixed with a chemical that is foul-tasting to canine predators such as wolves, coyotes, and domestic dogs. This novel behavior is generally observed to be very effective in defense; however, it appears to have no effect against predatory birds. [11] [12] [13] [14] [15]

Camouflage concealment through color or pattern

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis). Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.

Autohaemorrhaging or reflex bleeding is the action of animals deliberately ejecting haemolymph or blood from their bodies. If the animal has toxic compounds in its blood, then it may be an effective chemical defence mechanism.

Eyelid thin fold of skin that covers and protects the human eye

An eyelid is a thin fold of skin that covers and protects the human eye. The levator palpebrae superioris muscle retracts the eyelid, exposing the cornea to the outside, giving vision. This can be either voluntarily or involuntarily. The human eyelid features a row of eyelashes along the eyelid margin, which serve to heighten the protection of the eye from dust and foreign debris, as well as from perspiration. "Palpebral" means relating to the eyelids. Its key function is to regularly spread the tears and other secretions on the eye surface to keep it moist, since the cornea must be continuously moist. They keep the eyes from drying out when asleep. Moreover, the blink reflex protects the eye from foreign bodies.

Diet and decline

Federal horned toad pic crop.jpg

About 70% of the Texas horned lizard's diet is made up of harvester ants, though they supplement these with termites, beetles, and grasshoppers. In recent years, the species has declined by about 30% of its range, though it may be making a comeback.[ citation needed ] The decline is usually blamed on overuse of pesticides and the spread of nonnative, highly aggressive and fiercely territorial red imported fire ants. Both eradicate harvester ant colonies, destroying the lizard's principal source of food. The Texas horned lizard is now a protected species, and, in Texas, it is illegal to take, possess, transport or sell them without a special permit.

Red harvester ant species of insect

Pogonomyrmex barbatus is a species of harvester ant from the genus Pogonomyrmex. Its common names include red ant and red harvester ant. These large ants prefer arid chaparral habitats and are native to the Southwestern United States. Nests are made underground in exposed areas. Their diets consist primarily of seeds, and they consequently participate in myrmecochory, an ant-plant interaction through which the ants gain nutrients and the plants benefit through seed dispersal. Red harvester ants are often mistaken for fire ants, but are not closely related to any fire ant species, native or introduced.

Termite insect

Termites are eusocial insects that are classified at the taxonomic rank of infraorder Isoptera, or as epifamily Termitoidae within the cockroach order Blattodea. Termites were once classified in a separate order from cockroaches, but recent phylogenetic studies indicate that they evolved from close ancestors of cockroaches during the Jurassic or Triassic. However, the first termites possibly emerged during the Permian or even the Carboniferous. About 3,106 species are currently described, with a few hundred more left to be described. Although these insects are often called "white ants", they are not ants.

Beetle order of insects

Beetles are a group of insects that form the order Coleoptera, in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 species, is the largest of all orders, constituting almost 40% of described insects and 25% of all known animal life-forms; new species are discovered frequently. The largest of all families, the Curculionidae (weevils) with some 70,000 member species, belongs to this order. Found in almost every habitat except the sea and the polar regions, they interact with their ecosystems in several ways: beetles often feed on plants and fungi, break down animal and plant debris, and eat other invertebrates. Some species are serious agricultural pests, such as the Colorado potato beetle, while others such as Coccinellidae eat aphids, scale insects, thrips, and other plant-sucking insects that damage crops.

A University of Texas publication notes that horned lizard populations continue to disappear throughout the southwest despite protective legislation. The Texas horned lizard has disappeared from almost half of its geographic range. Population declines are attributed to loss of habitat, human eradication of the ant populations upon which the lizards prey, displacement of native ant populations by invading fire ants (aided by synergistic effects of native ant eradication), and predation by domestic dogs and cats. [16]

In 2014, the Center for Biological Diversity in Tucson, Arizona petitioned the Oklahoma Department of Wildlife Conservation to have the Texas horned lizard put on the endangered species list due to the massive declines of its population in Oklahoma, where it was once plentiful. The Center said it may later seek protection for the animal on a Federal level; it also said that reptiles in general are dying off at up to 10,000 times their historic extinction rate, greatly due to human influences. [17]

In Texas, the creature has been declared threatened and a breeding and reintroduction program has been started by the Fort Worth Zoo. Hatchlings are bred and released in targeted areas in the hope that with a large number of animals, enough will survive to grow the population in the wild. Typically in such reptile reintroduction programs, less than one percent of a female's offspring will survive in the wild to adulthood. [18]

Current research

Horned lizards are primarily studied by researchers at Texas Christian University, the nearby Fort Worth Zoo, and Dallas Zoo [19] with raw data and fieldwork done by state employees. Since 2010, the Dallas Zoo has been conducting a mark-and-recapture study on Texas horned lizards [20] on the Rolling Plains Quail Research Ranch, a 4,700-acre preserve located in Fisher County, Texas. Dallas Zoo researchers capture animals, tag them, collect data, and release them. [21] The project’s goals are aimed at shedding light on the life history, population density, and determining ecological conditions best suited for this threatened species. Further research toward their preservation is funded by sale of horned lizard "Keep Texas Wild" license plates. [22]

In addition, the Dallas Zoo and Houston Zoo are working to establish a captive colony [23] of animals with several key reproductive successes taking place in 2015.


Despite its fierce appearance, Texas horned lizards are extremely docile creatures.

The Texas horned lizard is a sunbather, and requires bright sunlight to produce vitamin D. Deprived of sunlight, the animal is unable to produce vitamin D and can suffer from vitamin deficiency. So, horned lizards are most often found along the side of roads or other open, rocky areas, where they can lounge and take in sunlight.

At night, the lizard buries itself in sand. [24]

Otherwise, horned lizards are most often found near harvester ant hills. Although they prefer to move very little, horned lizards can move quite fast if they feel a predator is in the area, and dart into thick grass and foliage to escape. Horned lizards are also excellent diggers, and can quickly burrow underground to escape threats.

Genetic mutation

Research aimed at preservation has revealed the Texas horned lizard is extremely genetically diverse, and isolated pockets of genetically distinct subspecies have been found throughout Texas. Though each of these subspecies is physically identical to all other subspecies, they are likely specifically adapted for the region in which they are found. This makes it difficult to know how one subspecies would survive if it were reintroduced into a new area.

The most numerous and widespread subspecies of Texas horned lizard is found in the Panhandle region of Texas. Other distinct subspecies have been identified in East Texas, the Hill Country, and along the coastline. It is not known whether these subspecies can reproduce with one another over the long term, making preservation of all of the subspecies even more crucial to the animals' preservation. It is also unknown whether any of these subspecies will show a particular resistance to the pesticides and fire ants threatening them.

In Native American religion and art

Some Native American peoples regard horned lizards as sacred. The animal is a common motif in Native American art in the Southwestern United States and Mexico. [7]

The Texas horned lizard is the state reptile of Texas [25] and, as the "horned frog," is the mascot of Texas Christian University [26] and can be seen in the university's seal.

Related Research Articles

Lizard suborder of reptiles

Lizards are a widespread group of squamate reptiles, with over 6,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic as it excludes the snakes and Amphisbaenia; some lizards are more closely related to these two excluded groups than they are to other lizards. Lizards range in size from chameleons and geckos a few centimeters long to the 3 meter long Komodo dragon.

Greater short-horned lizard Species of reptile

The greater short-horned lizard, also commonly known as the mountain short-horned lizard, is a species of lizard endemic to western North America. Like other horned lizards, it is often called a "horned toad" or "horny toad", but it is not a toad at all. It is a reptile, not an amphibian. It is one of seven native species of lizards in Canada.

Thorny devil species of reptile

The thorny devil, also known commonly as the mountain devil, thorny lizard, thorny dragon, and moloch, is a species of lizard in the family Agamidae. The species is endemic to Australia. It is the sole species in the genus Moloch.

Anti-predator adaptation mechanism developed through evolution that assist prey organisms in their constant struggle against predators

Anti-predator adaptations are mechanisms developed through evolution that assist prey organisms in their constant struggle against predators. Throughout the animal kingdom, adaptations have evolved for every stage of this struggle, namely by avoiding detection, warding off attack, fighting back, or escaping when caught.

Desert horned lizard species of reptile

The desert horned lizard is a species of phrynosomatid lizard native to western North America. They are often referred to as "horny toads", although they are not toads, but lizards.

Giant horned lizard species of reptile

The giant horned lizard is a species of phrynosomatid lizard which is endemic to the Pacific coast of southern Mexico. It is the largest horned lizard and is also the most slender. Like all lizards, the giant horned lizard is cold-blooded. It is able to survive in the desert. The spines on its back and sides are made from modified scales, whereas the horns on its head are true horns.

Coast horned lizard species of reptile

The coast horned lizard is a species of phrynosomatid lizard which can be found in Baja California Sur. The old classification included all three current species P. blainvillii, P. cerroense, and P. coronatum as a single species ranging from Baja California north to California's Sacramento Valley. It was previously considered to be a widely divergent species with over 6 subspecies in their relatively small range but is now classified as three distinct species. As a defense the lizard can shoot high pressure streams of blood out of its eyes if threatened.

The rock horned lizard or Ditmars' horned lizard is a species of phrynosomatid lizard endemic to Sonora in northern Mexico, south of the Arizona border. Bearing the shortest horns of all the horned lizards, it lives in thorn-scrub and deciduous Sinaloan woodlands. The rock horned lizard was "lost" to science for about 65 years. It has a unique habitat preference and limited distribution. It also had a very imprecise holotype locality record which made it difficult to locate. An extraordinary effort by Vincent Roth based on a cross-correlational analysis of gut contents from only three specimens led to its rediscovery.

Flat-tail horned lizard species of reptile

The flat-tail horned lizard is a species of lizard in the family Phrynosomatidae. A species of reptile, it is endemic to the Sonoran desert of the southwestern United States and northwestern Mexico. Its multiple adaptations for camouflage help to minimize its shadow. The species is threatened, with a restricted range under pressure from human activities such as agriculture and development, and is specially protected in the United States.

Roundtail horned lizard species of reptile

The roundtail horned lizard is one of the smaller species of horned lizard. Their specific epithet is from the Latin word modestum, meaning modest or calm. They are found in the United States, in western Texas, New Mexico eastern Arizona, southeastern Colorado and eight states in northcentral Mexico where they are referred to as "tapayaxtin".

Mexican Plateau horned lizard species of reptile

The Mexican Plateau horned lizard is a species of horned lizard. It is also known as the Chihuahua Desert horned lizard. The specific epithet, orbiculare, comes from the Latin adjective orbis, meaning "circular".

The northern desert horned lizard is a subspecies of the desert horned lizard, along with the southern desert horned lizard. It is often referred to as a "horny toad" due to its wide body and blunt snout, but it is not a toad.

The Mexican horned lizard is a horned lizard species native to Mexico. Horned lizards are sometimes referred to as "horned toads" or "horny toads", although they are not toads. Compared to other members of the horned lizards, little is known about this species.

The Gulf Coast horned lizard is a species of horned lizards native to Baja California, Mexico.

Regal horned lizard species of reptile

The regal horned lizard is a horned lizard species native to Mexico and the Southwest United States.

Skrjabinoptera phrynosoma is a parasitic worm in the phylum Nematoda, the most diverse of pseudocoelomates. Like many other parasites, the life cycle of S. phrynosoma is complicated and it involves two hosts – a lizard and an ant.

Pygmy short-horned lizard species of reptile

The pygmy short-horned lizard is a species of small horned lizard that occurs in the northwestern United States as well as in the southwestern Canada. Like other horned lizards, it is often called a "horned toad" or "horny toad," but it is not a toad at all. It is a reptile, not an amphibian.


Texas horned lizard in Beeville, Texas Texas Horned Lizard Beeville TX April 2011.jpg
Texas horned lizard in Beeville, Texas
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